Sample screening plant



Feb. 4, 1969 M. G. CURTIS 3,425,552

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2 3 3 a Q v u v m M O 1 E v v a INVENTOR. MERLE/VD 6. CUkTIJ i I v IFeb. 4, 1969 Q M. G. CURTIS 3,425,552

SAMPLE SCREENING PLANT Filed Sept. 12, 1966 Sheet 2 of 5 Hfikl-PNDCURTIS m F'W PTTYJ.

INVENTOR.

Feb. 4, 1969 v M. G. CURTIS 3,425,552

SAMPLE SCREENING PLANT Filed Sept. 12, 1966 Sheet 3 of 5 "FRI-FIND G.CllkThS HTTYS.

Feb. 4, 1969 M. G. cum-1s 3,425,552

SAMPLE SCREENING PLANT Filed sept. 12, 1966 Sheefi of5 az so 65 8o 48INVENTOR.

MPRLHND 6 60/2115 Feb. 4, 1969 I M. G. CURTIS 3,425,552

SAMPLE SCREENING PLANT Filed Sept. 12, 1966 5 Sheet 5 of s MHRLHND G.CURTIS INVENTOR.

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United States Patent 6 Claims Int. Cl. B07d 13/00 ABSTRACT OF THEDISCLOSURE A sample screening plant is described to permit mechanicalscreening and analysis of the relative size distribution of rockaggregate with maximum accuracy and testing uniformity. The screeningplant includes a plurality of stacked screens that are resilientlymounted on a pivot frame with a plurality of corresponding holdinghoppers positioned rigidly on the frame for receiving the outfeed fromthe corresponding screen. Each of the holding hoppers have ahydraulically operated gate that may be selectively operated to dump therock aggregate from the respective holding hopper into a weighing hopperthat receives and weighs the material.

'Ilhis invention relates to a sampler screening plant for rock aggregateof the type used in bulk quantities for large concrete 'projects such asdams and highways. It permits mechanical screening and analysis of asubstantial sample of material in a minimum amount of time, providingmaximum accuracy and testing uniformity.

At present, the sampling and'testing of aggregate is carried out bymanual methods wherein a small sample of aggregate is screened andweighed by techniques similar to those used in a laboratory. Thisprocedure is time consuming and requires skill on the part of the partyutilizing it, permitting human error to creep into the process at times.It also is time consuming, and difliculty in a particular sample mightnot be detected until a time at which the quantity of unacceptablematerial produced subsequent to the prior test of material has grownquite large. The present apparatus provides a mechanical device forscreening and weighing samples of aggregate in a short time. Iteliminates human factors which revolve about the time and amplitude ofshaking the screens and also provides ready adjustability to adapt theapparatus to proven degrees of accuracy.

It is a first object of this invention to combine, in a singleapparatus, a device for screening an aggregate sample and for separatelyholding each screened sample in a hopper for weighing purposes, togetherwith the necessary weighing machinery and transfer equipment forhandling the samples coming into and going out from the screening plant.The entire apparatus is relatively compact and mechanically simple. Itcan be readily handled by a single man.

Another object of this invention is to provide a sample screening plantwhich can be built to handle a relatively large sample 'of aggregate,commonly one thousand pounds.

Another object of the invention is to provide an apparatus which isadjustably to provide a high degree of screening efficiency undervariable conditions depending upon the nature and size of the aggregatebeing tested. Furthermore, the variations in vibration speed and inclineof the screens is desirable to permit clearance of material lodged inthe screens at the completion of a screening process.

'Ilhese and other objects will be evident from the following disclosure,taken together with the accompanying drawings which disclose a preferredform of the apparatus. It is to be understood that this form of thedevice is presented only by way of example and that minor modificationscould obviously be made without deviating from its basic scope andpurpose.

In the drawings:'

FIGURE 1 is a side elevation view of the screening plant;

FIGURE 2 is a plan view of the screening plant as seen from the top ofFIGURE 1;

FIGURE 3 is an enlarged sectional view as seen along line 33 in FIGURE2;

FIGURE 4 is an enlarged sectional view as seen along line 44 in FIGURE2;

FIGURE 5 is an enlarged sectional view as seen along line 55 in FIGURE4;

FIGURE 6 is an enlarged sectional view as seen along line 6-6 in FIGURE4; and

FIGURE 7 is an enlarged sectional view as seen along line 7-7 in FIGURE4.

Referring now to the drawings and specifically to FIG- URE 1, the gravelsample screening plant is supported on a frame generally designated as10 constructed of steel I beams and posts. A feed chute 11 directs theflow of a gravel sample from a batch plant (not shown) to a feed controlhopper 12 supported on frame 10. A hydraulic cylinder 13 is mounted in aframe 14 fixed to feed control hopper 12. Cylinder 13 selectively raisesor lowers a gate 15 (FIGURE 3). The gate 15 regulates the how ofmaterial into a vibrating feeder 16 carried on hopper 12.

The vibrating feeder 16 delivers material samples to a series of deckscreens 17 (FIGURE 3). Each deck screen 17 is supported on a series ofevenly spaced transverse bars 18 fixed to vertical side walls 20.Further support of the deck screens 17 is provided by longitudinal bars21 fixed between the transverse bars 18 (FIGURES 3 and 6). A verticalend plate 22, which connects the two vertical side walls 20, is providedwith an outwardly extending lip 19 to better direct the gravel samplefrom the vibrating feeder 16 to the deck screens. The deck screens 17are arranged to provide progressively finer screens from the top to thebottom of the series. A pair of transverse deflecting plates 23 arefixed between vertical side walls 20 to deflect rearwardly the particlesfalling from the screen above them to insure even screen utilization atall screen levels (FIGURE 3).

A pair of bearings 24 fixed to each side wall 20 serves to rotatablycarry a transverse shaft 25 (FIGURES 3 and 6). The shaft 25 extendsoutwardly from the side walls 20 to bearings 26 that rotatably carry theshaft ends 27. Each shaft end 27 is fixed to and is slightly offsetradially from the center of shaft 25 to provide an eccentricrelationship between the two shafts. One of the shaft ends 27 has fixedto it a pulley 28 that carries a drive belt 30 powered by a drive motor31. When motor 31 is operated, belt 30 rotates pulley 28, shaft ends 27,and shaft 25. As a result of the eccentric relation between shaft ends27 and shaft 25, this rotation causes the forwardly sloping deck screens17 to vibrate, thereby spreading and moving gravel through and along thedeck screens 17. The motor 31 is preferably provided with a variablespeed control to permit the variation of the number of vibrations perminute as required for different types of aggregate.

The bearings 26 which carry shaft 27 are supported on a pair oflongitudinal beams 32 located on either side of the deck screens 17(FIGURES l, 2, 4 and 6). Each beam 32 has fixed to its top surface apair of springs 33 that are adjustably fixed at their upper ends tobrackets 34 extending perpendicularly outward from side walls 20. Thesprings 33 aid in supporting the deck screens 17 without transmittingtheir vibration to other parts of the apparatus.

Each beam 32 has fixed to its forward end a bracket 36 with lower endsnotched to conform to a horizontal shaft on which which the beams 32 arepivotally carried (FIGURES 1, 2 and 4). The shaft 35 is fixed to avertical plate 37 (FIGURE 1) secured to frame 10. The opposite end ofeach beam 32 has fixed to it a pair of vertical and downwardlyprojecting cars 38 (FIGURE 3) which are pivotally attached to the endsof cylinder rods 40 of hydraulic cylinders 41. The lower ends ofhydraulic cylinders 41 are pivotally attached at 42 to frame 10.

The actuation of hydraulic cylinders 41 adjusts the angle of the deckscreens 17 from 2 to 12 above the horizontal about pivot shaft 35 toaccommodate different sizes and mixes of aggregates.

Also mounted on each beam 32 is a pair of angle irons 43 that providesupport for a diversion plate 44 positioned transversely above the deckscreens 17. When the deck screens 17 are in their lowest position ofincline, the diversion plate 44 serves to divert the flow of aggregatefrom the vibrating feeder 16 onto the infeed end of the deck screens 17.

A pair of short channels 45 are bolted to the lower surfaces of beams 32adjacent their forward ends and are respectively bolted to the verticalside walls 46 of a holding hopper 47 (FIGURE 4). This arrangement joinsthe holding hopper 47 rigidly to beams 32, so that it pivots about shaft35 with the deck screens 17. The holding hopper 47 is divided into onelarge forward compartment and seven smaller compartments by means oftransverse plates 48 fixed to vertical side walls 46 (FIGURE 3).

The upper part of each compartment is inclined toward the deck screen 17which will feed it the properly sized aggregate after it is separated bythe screening process. The aggregate is moved from the infeed end of thedeck screens 17 to the infeed ends of the holding compartments by theforward incline of the screens and by their vibrating action.

The lower end of each of the small compartments 53 has inclined sidewalls 52 to allow all of the aggregate to fall from the compartment onceit is opened (FIGURE 7). One of the inclined side walls 52 of eachcompartment 53 has fixed to it a pair of vertical plates 55 which areconnected at their upper ends by a bracket 56 (FIG- URES 4, 7). Thebrackets 56 mount a hydraulic cylinder 51 provided with cylinder rods57. A U-shaped bracket 58, fixed to the end of each cylinder rod 57, isattached to a gate slidably carried on guides 54 fixed to each verticalplate (FIGURES 4 and 7). When the hydraulic cylinder rod 57 is fullyextended (as seen in FIG- URE 7) the gate 50 closes an opening 60 in oneof the side walls 52 and prevents aggregate from leaving the compartment53. When hydraulic cylinder 51 is actuated, the gate is raised andaggregate is permitted to fall from the compartment 53. Each of theseven small compartments 53 of holding hopper 47 is closed by a gate 50which is raised and lowered by a separate hydraulic cylinder 51. Threeof the gates 50 and hydraulic cylinders 51 are located on one side ofthe holding hopper 47 and four are located on the opposite side of thehopper.

The large holding hopper compartment 61 has fixed to one of itstransverse walls 48 a bracket 67 that pivotally carries hydrauliccylinder 68 (FIGURES 1, 3 and 4). The cylinder rod 70 of hydrauliccylinder 68 has pivotally connected to it at 71 an arm 72. The arm 72 isfixed to one of a pair of clam jaws 73 which are pivotally carried onshafts 74 fixed to either side of hopper compartment 61. The clam jaws73 are connected by gears 75 fixed to each jaw on pivot shafts 74. Whenhydraulic cylinder 68 is actuated, the arm 72 is pulled upwardly and thejaws 73 pivot away from each other due to the meshing engagement ofgears 75, thus allowing aggregate to fall from the hopper compartment61.

The large holding hopper compartment 61 is provided with a vibratorscreen 62 at the top of its vertical portion (FIGURES 3 and 5). Thevibrator screen is constructed of evenly spaced longitudinal members 63and transverse members 64 which form a screen with large six inch squareopenings. A canopy 65 is mounted at the center of screen 62 to protect aconventional air vibrator 66 located under the canopy.

Fixed to either side of screen 62 are short rods that are pivotallycarried in bearings 81 fixed to side walls 46 of the holding hopper. Ahydraulic cylinder 84 is pivotally attached to one of the side walls 46by means of a bracket 85 (FIGURES 1 and 4). The cylinder rod 83 ofhydraulic cylinder 84 is pivotally connected to a crank arm 82 which isfixed to one of the rods 80. When hydraulic cylinder 84 is actuated thevibrator screen 62 pivots in bearings 81 spilling the aggregate toolarge to pass through the screen.

Located directly below the holding hopper 47 is scale hopper generallydesignated as 86. The scale hopper 86 is supported at its four cornersby vertical rods 87 which are pivotally connected to a pair ofhorizontal rods 88 located on either side of the hopper. The horizontalrods 88 are suspended from the frame 10 vertical rods 90. A series ofbeams and rods are connected to the horizontal rods 88 to form aconventional beam balance weighing system 91. The beam balance system isconnected to a graduated scale dial located in the control house 92. Thescale hopper 86 has attached to one side a frame 93 which mounts ahydraulic cylinder 94 which when actuated serves to raise and lower agate 95. The gate 95 closes an opening 96 in the scale hopper 86 throughwhich the aggregate passes after it has been weighed.

A waste conveyor 97 is located directly below scale hopper 86 and issupported on the frame 10. A three sided hopper 98 is attached to wasteconveyor 97 to keep the aggregate on the conveyor as it falls from scalehopper 86. The waste conveyor delivers the weighed aggregate to a wastepile after it is released from the scale hopper 86.

All controls for operation of the sample screening plant are containedin the control house 92. The operation of the screening plant beginswhen a sample of aggregate are contained in the control house 92. Theoperation of enters feed control hopper 12 from a batch plant (notshown). The hydraulic cylinder 13 is then actuated, raising the gate 15and allowing the aggregate to be spread on the deck screens 17 by thevibrating feeder 16. When the sample of aggregate falls on the deckscreens 17, the largest aggregate is retained on the top deck screen andis gradually moved toward the holding hopper 47 due to the inclinationand the vibration of the screens. Aggregate that is small enough fallsthrough the top deck screen and continues to fall until it is retainedby a screen with openings smaller than the aggregate size. The gauge ofthe deck screens 17 is progressively finer from top to bottom. Theconstant vibrating action of the deck screens 17 assists the passage ofvarious sized aggregate through the screens, and provides more completespreading and separation of the aggregate. The vibration of the deckscreens 17 along with their incline cause the aggregate to be graduallymoved forwardly toward holding hopper 47 while it is to be separated. Atthe end of the screening process, the motor 31 is set at its maximumspeed and the deck screens 17 are inclined at their maximum angle tocompletely clear the screens of any aggregate that may have becomelodged in the screens.

As the large aggregate that cannot pass through the top deck screen 17enters the largest compartment 61 of holding hopper 47 aggregateparticles larger than six inches square are held by vibrator screen 62.Aggregate smaller than six inches square passes through the screen 62and is retained in the compartment by closed jaws 73. Once all aggregatehas passed into the various holding hopper compartments, the jaws 73 areopened individually in succession by hydraulic cylinder 84. Theaggregate retained by each holding hopper compartment is then weighed inscale hopper 86 by operation of the beam balance system 91. The weightof the aggregate is registered on the graduated dial in control house92. After each sample of sized aggregate has been weighed, the hydrauliccylinder 94 is actuated, which raises gate 95 and allows the aggregateto fall onto waste conveyor 97. After all other weighing is completed,gate 95 is closed and the vibrator screen 62 is pivoted by actuation ofhydraulic cylinder 68, dumping its load of aggregate into the scalehopper 86 Where it is weighed and removed from the hopper.

One very important feature of the apparatus described above is the factthat the operator of the device can readily adjust the inclination ofthe deck screens 17 by utilization of hydralic cylinders 41, which pivotthe screens 17 and holding hoppers 47 in unison about the shaft 35.Before using the plant, it must be calibrated to match normallyacceptable standards of testing carried out by manual or laboratoryprocedures. A sample of aggregate must be separated and weighed bymanual methods and then fed through the apparatus described above, sothat the results can be compared. By doing so successively, and byadjustment of the inclination of the deck screens 17 and the speed ofrotation of the variable speed motor 31, the operator of the plant canmatch the laboratory test results and the test results of the mechanicaltesting plant. The inclination of the screens 17 can be noted, alongwith the rotational speed of motor 31, so that these factors can beduplicated each time that particular type of aggregate is being tested.Other types of aggregate used in a particular job might requiredifferent inclinations and different speeds of rotation to vibratescreens 17, but once the apparatus has been calibrated for a particulartype of aggregate, the operator can instantly adjust the device prior toa testing procedure, duplicating the desired degree of accuracy andrelating it to normally accepted manual methods. The versatility of theapparatus is apparent, since a single screening plant can quickly beadjusted to test anyone of several different aggregate mixes.Furthermore, at the completion of testing, the inclination of screens 17can be made a maximum and the speed of motor 31 can be increased todislodge any stones or particles trapped in the individual deck screens.Again, it is a simple matter to readjust the apparatus for the nextbatch of aggregate.

The entire testing process requires very little time and, since all ofthe steps are mechanical, can be carried out more promptly and withgreater frequency than is possible when using manual procedures.Furthermore, the test results are tabulated immediately and productionof aggregate can be adjusted or terminated if faulty sizing of particlesis detected. The lag between production and testing is minimized,eliminating unnecessary waste which occurs when the testing procedurerequires additional time, during which faulty production might continue.

Having thus described my invention, I claim:

1. In a sample screen plant for rock aggregate material:

a rigid supporting lframe work;

a pivotal frame pivotally mounted on the framework for movement about ahorizontal axis;

a plurality of sample screens resiliently mounted on said pivot frame inan upright stack with progressively finer screens from top to bottom,each screen being inclined downwardly perpendicularly to the horizontalpivot axis to an open outfeed end;

a plurality of holding hoppers rigidly mounted on said pivot frame, eachin open communication with the open outfeed end of a singlecorresponding sample screen for receiving the material from the openoutfeed end, each holding hopper being provided with a selectivelyoperable outlet;

a weighing hopper supported on the framework beneath the selectivelyoperable outlets of the holding hoppers for receiving and weighing thematerial discharged from the holding hoppers therefrom, said weighinghopper having a selectively operable outlet;

a first power means mounted on said pivot frame and operativelyconnected to said sample screens for vibrating said screens;

a second power means mounted on said framework and operatively connectedto said pivot frame to pivot said pivot frame to position the screens atdesired inclinations to the horizontal while the screens are beingvibrated to direct the material that is too large to pass through eachscreen to the corresponding open feed end;

a third power means supported on the framework and operatively connectedto the selectively operable outlets of the holding hoppers toselectively open said outlets to dump material from said holding hoppersinto the weighing hopper; and

a fourth power means supported on the framework and operativelyconnected to the selectively operable outlet of the weighing hopper toopen said outlet after the material is weighed.

2. In a sample screening plant as defined in claim 1 wherein the secondpower means adjusts the inclination of the sample screens between twodegrees and twelve degrees from the horizontal.

3. In a sample screening plant as defined in claim 1 wherein the samplescreens are resiliently mounted on the pivot frame by compressionsprings and wherein the first drive means includes an eccentric shaftrotata bly journalled in a concentric bearing and a radially offsetbearing.

4. In a sample screening plant as defined in claim 1 further comprisingdeflecting plates mounted transversely between sample screens to deflectmaterial falling toward the upper end of the immediately lower screen.

5. In a sample screening plant as defined in claim 1 wherein the holdinghopper corresponding with the outlet of the top sample screen contains ascreen therein for separating the rock aggregate having a diametergreater than six inches from the rock aggregate having a diameter lessthan six inches.

6. In a sample screening plant as defined in claim 1 wherein the thirddrive means includes a plurality of hydraulic cylinders operativelyconnected to corresponding selectively operable outlets of the holdinghoppers for selectively opening said outlets.

References Cited UNITED STATES PATENTS 2,312,477 3/1943 Pollitz 2093 292,782,926 2/ 1957 Saxe 209-239 X 2,925,177 2/1960 Troland 209-490 X3,077,266 2/1963 Plumb 2093 17 3,098,037 7/1963 Tonjes 209-237 X FOREIGNPATENTS 611,203 3/1935 Germany.

HARRY B. THORNTON, Primary Examiner.

R. HALPER, Assistant Examiner.

US. Cl. X.R. 209260, 317

